Production of alkylaromatics



May 27, l947- E. A. JOHNSON PRODUCTION OF ALKYLROMATICS Filed Feb. 29, 1944 Patented May 27;

2,421,331 y rnonUc'rIoN or ALxYLAnoMA'rros Everett A. Johnson, Park Ridge, Ill., aaslgnor to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application February 29, 1944, Serial No. 524,449

11 claims. (ci. 26o-671) This invention relates to the production of alkylaromatic hydrocarbons and relates more particularly to the production of monoalkylbeno zenes by the alkylation of benzene with oleflns such as ethylene and propylene.

Monoallwlbenzenes and particularly th'e lower boiling monoalkylbenzenes such as ethylbenzene or isopropylbenzene have been found to be valuyields from such processes but the low octane diluents contained in such fractions are not desirable aviation gasoline constituents.

It has been known for some time that the alkylbenzenes can be synthesized' by the alkylation of aromatic hydrocarbons with olefins in the presence of activating catalysts. In -such processes it is generally desirable that the charge bey rich in benrene and/or oleiins because oi the great reduction in reaction space, but when an excess of olens is used, polyalkylbenzenes are formed. Optimum cleanup of benzene from dilute benzene streams by simply alkylating to form the desired monoalkylbenzenes, however, is not the solution since the recycling of unreacted benzene to the alkylation zone is not possible because of the inert diluent.

.'It is an object of this invention to provide an improved process for the alkylation of aromatic hydrocarbons with olenic gases to produce optimum proportions of low boiling monoalkylbenzenes. Another object of my invention is to provide animprcved. process for the production of aviation fuel, including alkylaromat'ic hydrocarbons, by a combination of integrated steps. A still further object of my invention is to provide an improved process wherein hydrocarbons valuable for aviation fuels are prepared from refinery fuel gases and a benzene-containing fraction. Further objects and advantages will become apparent as the description of my invention proceeds.

Briey stated my invention contemplates a unitary process includingl the alkylation of an aro- 2 matic hydrocarbon stream' with olens by contacting in the presence of an alkylation catalyst such as phosphoric'acid, aluminum chloride hydrocarbon complex, or hydrogen fluoride under alkylation conditions of temperature, pressure and ratio of reactants. Propylene and/or ethylene, for example, may comprise the olefin charge to, produce cumene and ethylbenzene and polyisopropyland polyeth'ylbenzenes, respectively. The olefin feed may comprise concentrated oletlns or dilute fuel gases. The aromatic feed to the a1- kylation step comprises an alkylbenzene recycle fraction and or benzene. Relatively dilute benzene streams can be used, particularly when concentrated olens are fed to the allrylation.` The alkylbenzene recycle fraction is an intermediate the absorber-separator to scavenge benzene and to purge the diluent hydrocarbons from the dilute stream. The total aromatic streamincluding the recycled polyalkylbenzenes and the alkylation product is vrecovered as bottoms fromv the ,absorber-separator. This stream comprises essentially polyalk'ylaromatics and any benzene which was absorbed from any dilute benzene stream. The next step in my unitary process is/to subject this predominantly polyalkylbenzene fraction `to disproportionation in the presence of added benzene and a quantity of a catalyst similar to'- tion into the initial alkylation zone to produce additional polyalkylbenzenes or into the separator-absorber fornrecovery of the benzene and the purging of diluent hydrocarbons from'the system.

In one embodiment of my invention I employ oleiin-benzen mol ratios higher than one in order to effect optimum alkylation of the aromatics. Only by using excess olens can the benzene cleanup exceed about 50%. When 50% of the total benzene is alkylated approximately 75% of the alkylate is monoalkyland `25% is polyalkylbenzene. By 'increasing the olefin to aromatic mol ratio, the cleanup can be increased to 75% under which conditions the alkylate contains about equal amounts of monoand polyalkylbenzenes. Thus the use of a molar excess of olefxns produces substantial amounts of higher boiling polyalkylbenzenes unsuitable for use as a motor'or aviation fuel. By my process the lighter of this material is further alkylated, the heavier material is introduced into the separator-absorber at a high point, and the combined streams fed to the disproportionation zone.

The accompanying drawing diagrammaticaily illustrates apparatus suitable for carrying out one preferred embodiment of my invention and is in the form of a simplied now diagram.

Referring to the drawing,'a benzene stream, for example, such as that derived from naphthas and cycle stocks by thermal or catalytic cracking thereof or preferably by hydroformingnaphtha, usually hydroforming straight run naphtha, enters alkylator IIl by lines II and I2. The dilute benzene stream may contain between about 10% and about 75% or more benzene. A light polyalkylbenzene fraction recovered from the disproportionator I3 is supplied by line I4 as additional feed and in some instances `may comprise substantially the entire aromatic feed to alkylator IB. An olen, such as propylene, is introduced by line I5 in an amount such as to maintain a mol ratio ofxolen to aromatic fed to the alkylator Ill of between about one and about ve or higher, for example, above about 2.5. The oleiln stream may contain substantial amounts of diluting hydrocarbons such as light paraillns.

'I'he alkylator I0 can be any conventional reactor for contacting hydrocarbons and catalyst and suitably can be a tower containing a bed of supported catalyst, for example, phosphoric acid on kieselguhr. Other forms of catalytic contacting apparatus such as so-called-uid catalyst systems wherein a nely divided solid catalyst iis maintained in a highly dispersed phase or in a dense turbulent iiuent phase may be used. In the case ofhydrogen iluoride or aluminum chloride-hydrocarbon complexes, tower reactors, wherein a pool of catalyst is maintained, can be used.` The combined charge is fed at the rate of between 0.01 to 1.0, for example, below about 0.3 gallon per hour per pound of phosphoric acid catalyst within the reactor for maximum olefin and benzene cleanup. Reaction pressure aiects the oleiin and benzene cleanupl and a pressure of between about 50 and about 300 p. s. i. is contemplated. The temperaturewithin the alkylator -I is maintained within the range of between about 400 and about 600 F., for example, about 450 F. If desired, 0.5 to about 2% of feed can comprise an alcohol, which may correspond to the alkylating oleiln, to maintain the proper degree of hydration in the phosphoric acid catalyst, and

4 I0 with the oleilns and/or aromatics is contacted with a recycle polyalkylaromatic hydrocarbon stream supplied by line I8. .This fraction is higher boiling than is generally considered suitable or desirable in gasoline streams and may contain such aromatics as diethylbenzene, ethyltoluene. triethylbenzene, propyltoluene, etc. Extraneous polyalkylarcmatics can be introduced by line 33. The separator-absorber l1 is maintained at a pressure within the approximate range of about atmospheric to about 500 pounds per square inch and at temperatures Within the approximate range of to 150 F. The unabsorbed diluent gases, substantially oleiln'- and benzene-free, pass overhead through line 20 while the enriched \alkylbenzenes are withdrawn from absorber through line 2| and directed via line 22 to disproportionator I3.

The material removed by line 20 may comprise la cut boiling up to about 220 F. and can be subjected to a catalytic conversion wherein the diluent hydrocarbons are removed and a more concentrated benzene is recovered for recycle to the alkylation. Suitable catalysts are hydroforming and cracking catalyst. If desired the catalytic conversion can be the source of the dilute benzene stream, i. e., a hydroforming or a catalytic aromatizing of naphtha. 'I'hus the inert diluent and residual benzene is recycled to the source which may suitably be hydroforming.

The polyalkylbenzene cut or a fraction thereof in line 2| is then contacted in the presence of an alkylation catalyst with concentrated benzene introduced into the disproportionation reactor I3. for example, by line 23 and recycled from fractionator 30 by lines 24, 25 and 26.- Concentrated benzene sufficient for the disproportionation can be recovered from a portion of the benzene alkyl-v ation feed charged by line I I by azeotropic distillation or by .introducing into the absorber I1 by line 21. A portion of the recycle benzene can be bled into the absorber-separator I'I by lines 25 and 26 to remove diluents which might accumulate.

In the event that the alkylation is conducted with lower olefin ratios to aromatics including substantial proportions oi benzene the product inline 2l comprises substantially greater amounts of monoalkylbenzene and the entire stream may be introduced into a separator (not shown) for the recovery of a monoalkylbenzene cut boiling up to about 350 F. and of a heavier polyalkylbenzene cut. The lighter fraction-can be withdrawn for blending with a base stock since it will not contain substantial amounts of hydrocarbons boiling below about 220 F., or it can be introduced into the fractionator 30 for the recovery of monoalkylbenzene. Such an operation bypasses the disproportionator I3 with the result that optimum amounts of monoalkylbenzenes will result from the disproportionation of the predominantly polyalkylaromatic portion which 'is sent to I3.

The reaction in disproportionator I3 is essentially one of dealkylation of the polyalkylbenzene in the presence of excess benzene which in turn is alkylated primarily to monoalkylbenzene. The mol ratio of benzene to polyalkylbenzenes introduced into disproportionator I3 should be at least 1:1 and preferably greater than the number of mois of olefin attached as the alkyl groups to the polyalkylbenzenes. Higher temperatures such as those within the range of between about 500 and about '700 F., for example 650 F., are suitable with phosphoric acid alkylation catalyst and the catalyst employed therein shouldjbe at least as active as that usedinalkylator I0.

One mol of polyisopropylbenzene was disproportionated with two mols of benzene over solid example at about 200 F., and under pressures of between about 100 and 300 pounds per square inch. Two mols of benzene and one mol of diethylbenzene were maintained at 2052l0 F. in-

the presence of '7% aluminum chloride and HC1 was passed through the stirred mixture. The cooled products were separated into an upper layer representing 85% of the hydrocarbon and a lower catalyst layer. The hydrocarbon layer contained 42% benzene, 43% ethylbenzene and 15% diethylben'zene and heavier. It is contemplated that hydrogen iluoride can be used to eiIect a similar reaction at temperatures above alkylation temperatures and under suicient pressure to maintain the liquid phase.

The disproportionation product is withdrawn by line 29 from disproportionator I.3 and introduced into product fractionator 30. The products can be fractionatedto yield a benzene frction, a monoalkylbenzene fraction, an intermediate alkylbenzene fraction predominating in light polyalkylbenzenes and a heavy polyalkylbenzene fraction. The desired monoalkylbenzene cut is withdrawn from fractionator 30 by line 3 I. A benzene overhead cut ordinarily is recycled by lines 24 and 25 either to the disproportionation reactor I3 directly by line 26 or tothe separatorabsorber I1 by lines 25 and 28. The heavy polyalkylbenzene fraction is returned to absorber Il via line I8, while the intermediate alkylbenzene fraction comprising light polyalkylbenzenes is Withdrawn through line I4, and is preferably directed to alkylator I via lines II and I2. light alkylbenzene fraction can be withdrawnby line 32 for use, for example, as a solvent. The lighter polyalkylbenzenes added to the alkylator I0 are converted in alkylator I0 to higher boiling polyalkylbenzenes by olefins introduced at I as hereinbefore described. operation only the light polyalkylbenzenes are subjected to further alkylation and substantially only polyalkylbenzenes are introduced into the disproportionation zone. with benzene. Only the heaviest polyalkylbenzenes are employed as an absorbing medium, and loss of light products by the sweeping eilect of the entering gases is sub.- stantially eliminated. It is possible to use in the disproportionation a benzene cut having 60 to 100% benzene and to recycle the unreacted benzene fraction' until' the concentration becomes uneconomic at which time it can be-recycled to thealkylation zone I0 to be converted to monoand polyalkylbenzenes which are subsequently disproportionated in the disproportionator I3. If desired, the entire benzene fraction for disproportionation can be supplied via the separatorabsorber system. l

It is contemplated that the alkylator I0 and the disproportionator I3 can be used alternately for alkylation and disproportionation by provid- In this manner of l ing the necessary conduits and valves. Thus one can be used at a lower temperature to effect alkylation and then used at the higher temperature for disproportionation or the sequence can be reversed.

It should be; understoodlthat the alkylation and disproportionation steps may comprise two or more stages and that additional apparatus can be supplied when-necessary, for-example, when using aluminum ychloride hydrocarbon complex or hydrogen fluoride as the catalyst. In that event the alkylation zone I0 and disproportionator' I3 will include an alkylator provided with means for withdrawal of`catalyst and reactants into a settling chamber from which the catalyst is recycled to the alkylator, the hydrocarbon fraction separated, and scrubbed with dilute caustic before introduction into the absorber I1 or prodv uct fractionator 30. Spent catalyst may be withdrawn from either the alkylator or disproportionator. Likewise catalyst used in either zone may be transferred to the other. The absorberseparator system I1 can be in stages, either series or parallel. Monoalkylbenzene trapout can be provided on I1.

From the foregoing it will be apparent that I have attained the objects of my invention and have provided a new process for the production of optimum quantities of monoalkylbenzenes by a combination of integrated steps wherein aro-v matics are alkylated with oleflns to produce higher boiling aromatics, alkylaromatics heavier than the desired monoalkylbenzene are cut into light and heavy fractions, the light is further alkylated in the first step with an volefin stream and goes to an absorber-separator where it is scrubbed with the heavy polyalkylaromatic. The combined streams of alkylaromatics go to a disproportionator for the production of additional monoalkylbenzene. 'I'hus an optimum fraction is further alkylated to eiect optimum olefin and benzene cleanup and optimum feed is provided for the disproportionation.

Although I have described my process with special referenceto embodiments thereof it should be understood that this is by way of illustration only and not by limitation and that I intend to be limited only to the extent set forth in the appended claims. Moreover various details such `as pumps, heat f exchangers, automatic control Iclaim: y

1. A process for the production of monoalkyl benzeneswhich comprises supplying an `olefincontaining stream and lalkylated mononuclear aromatics to an alkylation zone, further alkylating said aromatics with said olefins in the vpresence of an alkylation catalyst within said zone, withdrawing the alkylation products from said zone, introducing the alkylation products and unreacted hydrocarbons into a gas separation zone, introducing into said separation zone a relatively cool polyalkylated aromatic liquid fraction hereinafter derived, withdrawing gases overhead' from said separation zone recovering a combined liquid stream from said separation zone comprised essentially of polyalkylated aromatics, commingling benzene with said polyalkylated mononuclear'aromatics contacting said polyalkylated aromatics and a. molar excess of benzene with another quantity of said alkylation catalyst, maintaining the temperature within `said contacting zone substantially above that maintained in the 7 alkylation zone whereby substantial proportions of said polyalkylaromatic and of said benzene are converted to monoalkylaromatic hydrocarbons, withdrawing the products from said second contacting step, recovering atv least one monoaromatic-containing stream to an alkylation zone,

alkylating said aromatics with said olens Within said zone in the presence of a phosphoric acid alkylation catalyst, withdrawing the alkylation products from said zone, introducing the alkylation products and unreacted hydrocarbons into a gas separation zone, introducing into said separation zone a polyalkylated mononuclear aromatic liquid fraction hereinafter derived, withdrawing gases overhead from said separation zone, recovering a combined liquid stream from said separation zone comprised essentially of polyalkylated aromatics, commingling benzenewith said polyalkylated mononuclear aromatics reacting said polyalkylated aromatics and a molar excess of benzene in the presence of another quantity of phosphoric acid alkylation catalyst, maintaining the temperature during said reaction substantially above that maintained in the alkylation zone whereby substantial proportions of `said polyalkylaroniatic and of said benzene are converted to monoalkylaromatic hydrocarbona withdrawing the products from said second reaction step, recovering from the reaction productI at least one fraction suitable as an aviation gasoline constituent, an intermediate alkylaromatic fraction and a heavy polyalkylaromatic fraction, and supplying said intermediate alkylaromatic fraction to the first-mentioned alkylation step and at least a portion of said heavy fraction tothe separation zone. y

3. A lprocess for the production of alkylbenzenes in the aviation gasoline boiling range which comprises suplying an olen and a stream of hydrocarbons including mononuclear aromatic's to an alkylation zone in a mol ratio of oleiin to aromatic of at least 1:1, reacting the said olen and aromatica in the` presence of an alkylation catalyst within said zone under alkylation conditions of temperature and pressure, withdrawing the reaction products from said zone, introducing the reaction products at a low point in a separation zone, introducing a polyalkylated aromatic fraction hereinafter derived into said separation zone at a relatively high point therein, withdrawing the gases overhead from said separation zone, withdrawing a liquid stream of polyalkylated aromatics from said separation zone. commingling benzene with said polyalkylated mononuclear aromatics, contacting in the presence of another quantity of said alkylation catalyst said reaction products together with sufllcient added benzene to give a ratio of total mononuclear aromatic hydrocarbons to alkyl groups of greater than 1:1, maintaining the temperature within said second contacting zone substantially above that maintained in the alkylation zone vwhereby substantial proportions of said polyal- 'alkylation catalyst to produce predominantlyl to monoalkylbenzene, withdrawing the. conversion products from said second contacting zone, separating said conversion products into a benzene fraction, a monoalkylbenzene fraction, an intermediate alkylaromatic fraction and a heavy polyalkylarornatic fraction, introducing said heavy alkylaromatic fraction into the aforemena tioned separation zone, and supplying at least a portion of the intermediate alkylaromatic iraction to the mst-mentioned alkylatlon'.

4. A process for the production of monoalkylaromatic-hydrocarbons in the aviation gasoline boiling range which comprises subjecting an olen stream diluted with light parains and a stream of .hydrocarbons including mononuclear alkylaromatics to alkylation in the 'presence of an polyalkylaromatics,v withdrawing the reaction products and unreacted hydrocarbons from said alkylation, introducing the reaction products and unreacted hydrocarbons into a gas separation zone, introducing a polyalkylated aromatic liquid fraction hereinafter derived into said separation zone at a relatively high point therein, withdrawing diluent hydrocarbons loverhead from said separation zone, withdrawing from said separation zone a liquid stream of -polyalkylated aromatics, introducing benzene and said polyalkylated aromatics into a second contacting zone, contacting said polyalkylaromatics together with said benzene in the presence of another quantity of said alkylation catalyst in a mol ratio of benzene nucleus to alkyl group of greater than 1`:1 in mid second contacting step whereby substantial proportions of said polyalkylaromatic and of said benzene are-disproportionated to produce monoalkylaromatic hydrocarbons, withdrawing the -products from said second contacting step, recovering from said products a benzene fraction, a monoalkylbenzene fraction, an intermediate alkylaromatic fraction and a heavy polyalkylaromatic fraction, introducing said heavy alkylaromatic fraction into the aforementioned gas separation zone, and supplying at least a portion o! the intermediate alkylaromatic fraction to the first-mentioned alkylation step.

5. A process for the production of monoalkylaromatic hydrocarbons in the aviation gasoline boiling range which comprises subjecting oletlnic and aromatic hydrocarbon fractions in 9; mol ratio of olefin to aromatic of .at least 1:1 to alkylation in the presence of an alkylation catalyst, introducing the reaction products and a gaseous benzene-containing stream at a low point into a gas separation zone, introducing into-said separation zone at a relatively high point therein polyalkylated aromatic fraction hereinafter derived, withdrawing gases overhead from said separation zone, withdrawing a combined liquid stream of benzene and polyalkylated aromatics from said separation zone, reacting said stream in the presence of another quantity of said alkylation catalyst in asecond contacting zone wherein the mol ratio of benzene to alkyl is greater than 1:1, maintaining the temperature during said second reaction substantially above that maintained in the alkylation step whereby substantial proportions of said .polyalkylaromatic and of said benzene are converted to monoalkylaromatic hydrocarbons, withdrawing the conversion products from said second contacting zone, separating said conversion products into a benzene fraction, a monoallgylbenzene fraction, an intermediate alkylaromatic fraction and a heavy polyalkylaromatic fraction, introducing said heavy alkylaromatics in the presence of an alkylation catalysty within said zone under alkylation conditions to produce alkylated mononuclear aromatics of higher -boiling point, introducing the reaction products and unreacted hydrocarbons at a W point' into a gas separation zone, introducing into said separation zone at a relatively high point therein a second polyalkylated aromatic fraction hereinafter derived, withdrawing gases overhead yalienati matic. fraction into the aforementioned separa- 8. A process for the production of monoalkylaromatic hydrocarbons in the aviation-gasoline boiling range which comprises the vsteps of subjecting oleflnic and mononuclear aromatic hydrocarbon fractions to alkylationl in the presence of an alkylation catalyst, introducing the alkylation products and a gaseous benzene-containing n stream at a low point into a gas separation zone,

from said separation zone, withdrawing a combined liquid stream of polyalkylated aromatics from said separation zone, introducing benzene and said polyalkylaromatics into a second conintroducing into said separation' zone at a relatively high point therein a polyalkylated mononuclear aromatic fraction hereinafter derived,

withdrawing gases overhead from said separation zone, withdrawing a combined stream of benzene and liquid polyalkylaromatics from saidseparation zone, reacting said stream in the presence of another quantity of said alkylation catalyst in a second contacting zone, maintaining the tem- .perature during. said second reaction' substantially above that maintained in the alkylation step whereby substantialproportions of said polyalkylaromatic and of said benzene are converted to monoalkylaromatic hydrocarbons, withdrawing the conversion products from said second contacting zone, contacting said reaction products together with additional amounts of a benzene fraction with another quantity of ksaid alkylation catalyst in said second contacting zone, maintaining the temperature within said second contacting zone substantially above that maintained in the alkylation zone whereby substantial proportions of said polyalkylaromatic and of said added aromatic are converted to monoalkylaromatic hydrocarbons, withdrawing the conversion products from said second contacting zone, recovering from said conversion products a benzene fraction, a monoalkylbenzene fraction, an intermediate alkylaromatic fraction and a heavy polyalkylaromatic fraction, supplying said heavy alkyiaromatic fraction to the aforementioned separation zone, subjecting at least a portion of the intermediate alkylaromatic fraction to the iirst-mentionedalkylation, and recycling the benzene fraction to said second contacting step. i

7. A process for the production of monoalkylbenzenes which comprises supplying oleiins and tacting zone, separating said conversion products to include at least a monoalkylbenzene fraction and a heavy polyalkylaromatic fraction, and supplying at least a portion of said h'eavy alkylaromatic fraction to said gas separation zone.

9. A process for the production of alkylbenzenes which comprises supplying mononuclear aromatics and olens to an alkylation zone, alkylating said aromatics with at least a portion of said olefins 'in the presence of an alkylation catalyst within said zone, withdrawing the total alkylation product stream from said zone including liquid alkylation products and unreacted hydrocarbons, introducing liquid alkylation products and .unreacted hydrocarbons at a low point into an absorber zone, introducing a relatively cool polymononuclear aromatics to an alkylation zone,

alkylating said aromatics with said olens in the presence of an alkylation catalyst within said zone, withdrawing the alkylation products from said zone together with unreacted hydrocarbons, introducing the alkylation products and unreacted hydrocarbons into a gas separation zone,

introducing into said separation zone a relatively cool polyalkylated mononuclear aromatic liquid fraction hereinafter derived, withdrawing gases overhead from said separation zone, recovering a j combined liquid stream from said separation zone comprising essentially polyalkylated aromatics introducing benzene and said polyalkylaromatics into a conversion Zone, contacting said poly alkylated aromatics and a molal excess of said benzene in the presence of another quantity of said alkylation catalyst at a higher'temperature than employed in the alkylation whereby substantial proportions of said polyalkylaromatic and of said benzene are converted. to monoalkylbenzene, recovering a monoalkylbenzene fraction, an intermediate alkylaromatic fraction, and a heavy polyalkylaromatic fraction from the conversion products, and supplying at least a portion of said heavy polyalkylaromatic fraction to said gas separation step.

alkylated aromatic liquid fraction at a high' point in said absorber zone, withdrawing overhead from said absorberzone a gaseous fraction, recovering a combinedliquid stream from said absorber stepl comprising essentially polyalkylated mononuclear aromatics and absorbed hydrocarbons, introducing benzene and said polyalkylated mononuclear aromatics into a conversion zone, contacting said polyalkylated aromatics with another quantity of said alkylation catalyst in the presence of a molal excess of said benzene within said conversion zone whereby substantial proportions of said polyalkylaromatic and of said benzene are converted to monoalkylaromatic hydrocarbons, withdrawing the products from said second catalytic contacting step, recovering a monoalkylbenzene fraction, an intermediate liquid alkylaromatic fraction, and a heavy polyalkylaromatic fraction, supv plying at least a portion of said intermediate alkylaromatic fraction to the first-mentioned alkylation step, and supplying at least a portion of said heavy polyalkylaromatic fraction to said absorption step.

10. A process for the production of monoalkylaromatic hydrocarbons comprising the steps of alkylating a mononuclear aromatic hydrocarbon with concomitant dealkylation of a polyalkylaromatic hydrocarbon in the presence of an alkylation catalyst under alkylation conditions adapted to yield both mono and polyalkylaromatic hydrocarbons, separating from th'e reaction product a, monoalkylaromatic hydrocarbon fraction and relatively high and relatively low boiling fractions of polyalkylated mononuclear aromatic hydrocarbons, alkylating at least -a portion of the relatively low boiling polyalkylaromatic hydrol carbons with olenns from a 'dilute stream `to produce high boiling polyalkylated mononuclear aromatics, contacting a gas stream containing re. actant hydrocarbons with at least a portion of the relatively' high boiling polyalkylbenzene whereby reactant hydrocarbons are adsorbed therein, and supplying said high boiling polyalkylated aromatic hydrocarbon fraction to said first alkylation step.

11. A process for the production of predominately monoalkyibenzene which comprises reactingan olefin-containing gaswith a hydrocarbon mixture consisting essentially of benzene and of relatively low boiling polyalkylbenzenes produced in the system, said reaction being conducted in the presence of an alkylation catalyst under conditions to yield predominately polyalkylbenzenes, absorbing benzene in a fraction of relatively high boiling polyalkylbenzenes produced in the system, reacting the mixture of polyalkylbenzenes and benzene with a second quantity oi similar alkylation catalyst at a higher temperature than employed in th'e rst alkylation, recovery from the second alkylation an alkylate containing substantial amounts of monoalwlbenzene, together with a smaller proportion of polyalkylbenzene than in the alkylate from the nrst alhiationzone,

step, respectively.

EVERETT A. JOHNSON.

A 5 REFERENCES CITED The following references are ot record in the iile of this patent:

, UNrrnn STATES PATENTS Number Name Date 2,010,948 Eglon Aug. 13, 1935 2,010,949 Egioi Aug. 13, 1935 2,222,632 Sachanen et al. Nov. 26, 1940 2,290,211 Schaad July 21, 1942 2,335,596 Marschner Nov. 30, 1943 2,338,711 DOuville et al Jan. 11, i944 2,238,594 Malishev Apr; 15, 1941 1,953,702 Davidson Apr. 3, 1934 l OTHER REFERENCES Newton Polyisopronylbenzenes I. Preparatives and Properties Journal American Chemical Society, 65:320-323, March 1943 (4 pages). (Pat. 01I.Library.) 26o/671. 

